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Subject[PATCH 005 of 10] md: raid1: Fix restoration of bio between failed read and write.

When performing a "recovery" or "check" pass on a RAID1 array,
we read from each device and possible, if there is a difference or a
read error, write back to some devices.

We use the same 'bio' for both read and write, resetting
various fields between the two operations.

We forgot to reset bv_offset and bv_len however.
These are often left unchanged, but in the case where there is an
IO error one or two sectors into a page, they are changed.

This results in correctable errors not being corrected properly.
It does not result in any data corruption.

Cc: "Fairbanks, David" <David.Fairbanks@stratus.com>
Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./drivers/md/raid1.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff .prev/drivers/md/raid1.c ./drivers/md/raid1.c
--- .prev/drivers/md/raid1.c 2008-05-19 11:03:05.000000000 +1000
+++ ./drivers/md/raid1.c 2008-05-19 11:02:55.000000000 +1000
@@ -1284,6 +1284,7 @@ static void sync_request_write(mddev_t *
rdev_dec_pending(conf->mirrors[i].rdev, mddev);
} else {
/* fixup the bio for reuse */
+ int size;
sbio->bi_vcnt = vcnt;
sbio->bi_size = r1_bio->sectors << 9;
sbio->bi_idx = 0;
@@ -1297,10 +1298,20 @@ static void sync_request_write(mddev_t *
sbio->bi_sector = r1_bio->sector +
conf->mirrors[i].rdev->data_offset;
sbio->bi_bdev = conf->mirrors[i].rdev->bdev;
- for (j = 0; j < vcnt ; j++)
- memcpy(page_address(sbio->bi_io_vec[j].bv_page),
+ size = sbio->bi_size;
+ for (j = 0; j < vcnt ; j++) {
+ struct bio_vec *bi;
+ bi = &sbio->bi_io_vec[j];
+ bi->bv_offset = 0;
+ if (size > PAGE_SIZE)
+ bi->bv_len = PAGE_SIZE;
+ else
+ bi->bv_len = size;
+ size -= PAGE_SIZE;
+ memcpy(page_address(bi->bv_page),
page_address(pbio->bi_io_vec[j].bv_page),
PAGE_SIZE);
+ }

}
}

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